SOLVED

21) A 1.50 L buffer solution is 0.250 M in HF and 0.250 M in NaF. Calculate the pH of the solution after the addition of 0.0500 moles of solid NaOH. Assume no volume change upon the addition of base. The Ka for HF is 3.5 × 10-4. A) 3.34 B) 3.46 C) 3.57 D) 3.63 E) 2.89 22) A 1.50 L buffer solution is 0.250 M in HF and 0.250 M in NaF. Calculate the pH of the solution after the addition of 0.100 moles of solid NaOH. Assume no volume change upon the addition of base. The Ka for HF is 3.5 × 10-4. A) 3.22 B) 3.82 C) 3.69 D) 3.09 E) 4.46 23) Which of the following is true? A) An effective buffer has a [base]/[acid] ratio in the range of 10 – 100. B) A buffer is most resistant to pH change when [acid] = [conjugate base] C) An effective buffer has very small absolute concentrations of acid and conjugate base. D) A buffer can not be destroyed by adding too much strong base. It can only be destroyed by adding too much strong acid. E) None of the above are true. 24) Define buffer capacity. A) Buffer capacity is the amount of acid or base that can be added to a buffer without destroying its effectiveness. B) Buffer capacity is the amount of acid that can be added until all of the base is used up. C) Buffer capacity is the amount of base that can be added until all of the acid is used up. D) Buffer capacity is the amount of acid that can be added until all of the acid is used up. E) Buffer capacity is the amount of base that can be added until all of the base is used up. 25) Which of the following is true? A) The equivalence point is where the amount of acid equals the amount of base during any acid-base titration. B) At the equivalence point, the pH is always 7. C) An indicator is not pH sensitive. D) A titration curve is a plot of pH vs. the [base]/[acid] ratio. E) None of the above are true. 26) When titrating a strong monoprotic acid with KOH at 25°C, the A) pH will be less than 7 at the equivalence point. B) pH will be greater than 7 at the equivalence point. C) titration will require more moles of base than acid to reach the equivalence point. D) pH will be equal to 7 at the equivalence point. E) titration will require more moles of acid than base to reach the equivalence point. 27) When titrating a weak monoprotic acid with NaOH at 25°C, the A) pH will be less than 7 at the equivalence point. B) pH will be equal to 7 at the equivalence point. C) pH will be greater than 7 at the equivalence point. D) titration will require more moles of base than acid to reach the equivalence point. E) titration will require more moles of acid than base to reach the equivalence point. 28) When titrating a monoprotic strong acid with a weak base at 25°C, the A) pH will be 7 at the equivalence point. B) pH will be greater than 7 at the equivalence point. C) titration will require more moles of the base than acid to reach the equivalence point. D) titration will require more moles of acid than base to reach the equivalence point. E) pH will be less than 7 at the equivalence point. 29) A titration of a weak acid gives an equivalence point of 9.18. The pKa of the acid is A) 9.18. B) 7.00. C) 4.59. D) 2.50. E) 6.28. 30) A 100.0 mL sample of 0.18 M HClO4 is titrated with 0.27 M LiOH. Determine the pH of the solution before the addition of any LiOH. A) 1.74 B) 1.05 C) 0.74 D) 0.57 E) 1.57